1. Field of the Invention
This invention relates to the separation of mononuclear cells from whole or diluted blood, and more particularly relates to a blood separation device and a method of separating blood components using such a device.
2. Description of the Prior Art
A well known blood separation device on the market today includes a blood collection tube containing an aliquot of a newtonian gel and an aliquot of a liquid density medium, such as Ficoll-Paque (.TM.). The newtonian gel acts as a barrier between the liquid density medium and a sample of blood placed in the tube atop the gel. When the tube is centrifuged, the liquid density medium acts to separate the mononuclear cells from the other blood components.
The conventional blood separation device described above works well for clinical laboratory applications, where a blood sample is placed in the tube and immediately centrifuged to separate out the targeted blood components. The device is not intended for use as, nor can it function as, a shippable blood separation device, i.e., such as where the physician draws a blood sample into the collection tube and sends it to a laboratory for centrifugation or further processing.
The reason why such devices cannot be shipped is that both the gel and the density medium are liquids and will not retain their pre-processed positions in the tube. Although each is immiscible with respect to the other, they will run in the tube when the tube is placed on its side. Accordingly, when the device is in such a position or if the device is disturbed, the newtonian gel may no longer be in position between the liquid density medium and a blood sample contained in the tube, and thus may no longer act as a barrier between the two. The blood sample will mix with the liquid density medium and affect its blood separation characteristics, namely its specific gravity or density, and consequently its ability to properly separate the mononuclear cells from the other components of the blood sample.